The invention relates to a method for controlling a pneumatic or electropneumatic service brake device of a vehicle.
In the method a driver braking demand is imparted through actuation of a service brake actuation element of a service brake valve device of the brake device. As a result of actuation of the brake actuation element, at least one control piston of the service brake valve device is subjected to load with a first actuation force and the control piston directly or indirectly controls at least one double-seat valve, which comprises an inlet seat and an outlet seat, in order to generate a pneumatic brake pressure or brake control pressure in at least one pneumatic service brake circuit of the service brake device.
The invention also relates to a service brake valve device for a pneumatic or electropneumatic vehicle service brake device, having a service brake actuation element which is actuable by a driver in a manner dependent on a driver braking demand. In a manner dependent on an actuation of the service brake actuation element, a pneumatic brake pressure or brake control pressure is input into at least one port for a pneumatic service brake circuit such that a first actuation force is applied to the at least one control piston. At least one double-seat valve which is controlled directly or indirectly by the at least one control piston and which comprises an inlet seat, which is connected to a port for a compressed-air supply, and an outlet seat, which is connected to a pressure sink, in a manner dependent on the control connects the at least one port for the pneumatic service brake circuit either to the port for the compressed-air supply or to the pressure sink.
Such a service brake valve device which is for example of single-circuit configuration, that is to say which controls one pneumatic brake circuit, is known from German patent document no. DE 42 32 492 A1.
Also known from the prior art are service brake valve devices with two pneumatic circuits, for example a front-axle brake circuit and a pneumatic rear-axle brake circuit. Furthermore, a service brake valve device of said type, which is then electropneumatic or footbrake module may also be supplemented by a purely electrical circuit which controls a primary electropneumatic brake circuit, wherein then, the two pneumatic brake circuits are used merely redundantly. Purely pneumatic service brake valve devices are accordingly for purely pneumatic service brake devices, and electropneumatic service brake valve devices or footbrake modules are for electropneumatic service brake devices or for EBS (electronically regulated brake systems).
All of these service brake valve devices from the prior art have in common the fact that, in their pneumatic ducts to which in each case one pneumatic service brake circuit is connected, they generate merely a brake pressure or brake control pressure which is dependent on an actuation of the brake actuation element, for example of a footbrake pedal.
On the other hand, driver assistance systems such as drive slip regulation systems (ASR), emergency braking assistants (AEBS), adaptive cruise control systems (ACC) or driving dynamics regulation systems (ESP) which vary, modulate or shut off with the aid of which the brake pressure or brake control pressure output by the service brake valve to the wheel brake cylinders, have, in part, existed for some time. In the case of ASR, for example, by way of ASR valves connected into the brake pressure lines between the corresponding duct of the service brake valve and the respective brake cylinders at driven axles, either the brake pressure output by the respective duct of the service brake valve device is input into the respective wheel brake cylinder, or else compressed air is supplied at a certain supply pressure from a compressed air storage vessel in the event of excessive drive slip.
Manipulation or variation of the brake pressure or brake control pressure in a manner dependent on driving operation conditions and secondary to the service brake valve device therefore firstly requires a certain outlay.
Secondly, a disadvantage of conventional ASR systems is that the brake pressure can be only controlled and not regulated by way of ABS pressure control valves, and said brake pressure can thus correspond to a setpoint pressure only to a limited extent. Also, different brake pressures can be set on the right-hand side and on the left-hand side of the vehicle, which may be noticeable in particular in the event of light braking interventions such as are often necessary for example in the case of an adaptive cruise control system (ACC).